Corrosion inhibitor composition



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Patented Aug. 21, 1951 amass CORROSION INmITOR COMPOSITION No Drawing. Application June 3, 1950, Serial No. 166,059

16 Claims.

i This invention relates to corrosion inhibitors and more particularly to corrosion inhibitors for aqueous metals.

Stabilized rosin amines such as hydrogenated rosin amines and dehydrogenated rosin amines are known to have the property of inhibiting corrosion of metal surfaces when applied to the surfaces in an unctuous solvent. Although these stabilized rosin amines and their salts have been found useful in unctuous solvents, they have not been found to be suitable per se as inhibitors of corrosion in aqueous solutions as in mineral acid solutions used in the cleaning of metals. Moreover, the amines themselves have not been satisfactory in neutral or alkaline water. Certain derivatives of stabilized rosin amines such as the ethylene glycol ethers of the ethanol rosin amines are, on the other hand, shown in copending application of Edward A. Bried, Serial No. 39,801, filed July 20, 1948, now U. S. 2,510,063, to be highly efllcient inhibitors for mineral acid solutions.

Now in accordance with this invention, it has been found that aqueous compositions normally corrosive to metal surfaces are inihibited toward corrosion of such metal surfaces when they contain dissolved or dispersed therein in small amounts a composition consisting of to 50% of a primary rosin amine and a. complement of a material of the formula RNH( CHzCHzO) mH solutions which normally corrode having a molecular weight between about 500 and about 2000, where R is a radical selected from the group consisting of abietyl, hydroabietyl, and dehydroabietyl and where m is an integer such that the molecular weight is within the above-designated range. The inhibitor compositions of this invention are particularly effective as inhibitors for mineral acids such as hydrochloric acid used in oil well acidizing and in boiler cleaning. Their effectiveness in inhibiting corrosion of ferrous metals by such mineral acids is much greater weight for weight than the efiectiveness of any of the components taken separately. There is thus a synergistic effect in the compositions as shown hereinafter in the examples which illustrate the use of the compositions of this invention.

The technique of carrying out the tests was as follows:

To samples of 15% hydrochloric acid were added in an amount of 0.2% by weight of the acid the materials designated in the tables. The inhibited acids were then thoroughly stirred at 165 F. to effect complete dispersion of the added inhibitor materials. To each of these solutions was added a weighed freshly polished low carbon steel plate (2 inches square) at 165 F. and the solutions were maintained at that temperature for four hours. The plates were then weighed for weight loss as a measure of corrosion. For comparison, an uninhibited hydrochloric acid solution was also tested. The per cent corrosion is calculated by dividing the percent weight loss of the plate in the inhibited acid by the per cent weight loss of the plate in the uninhibited acid. The results are recorded in the table.

Table Per Cent Cor- Inhibitor Composition g fi gg g Amount 01- MoLWt. Per Cent 0.2% 0.1%

1 Dehydrogenated rosin e 283 100 2.12 1.97 2 Polyethylene ycol ether of monoet ol dehydrogenated rosin amino l, 620 100 2. 97 8 Pol ethylene glycol at er of monoethanol dehydrogenated rosin amine l, 210 100 2. 73 4 Polgethylene glycol ct er of monoethanol dehydrogenated msin amino 795 100 2. l0 5 Polyethylene glycol et er oimonoethanol dchydrogenated rosin amino 695 100 l. 28 6 Polyethylene glycol et er of monoethanol dehydrogenated rosin amine 500 100 0. l. 11 {Compound 1... 283 15 0 s e" i2 om an s {g g g gg 1,2 0.96 1.50

om un 9 {g g g 2 3 ,{3 0.14 1.21

om un 10 gg gag 3g 0.86 1.10

cm un 11 gg g 0.80 0.12

cm un 12 {oomgunc 1,620 13 Compound 283 6 l 31 Compound 1,210 95 14 Compound 283 5 1 u Compound 4-.- 795 95 15 {Compound 1..- 283 5 1 02 Compound 6... 695 06 Similar tests have shown that there is a synergistic effect in the inhibitor properties of ordinary rosin amine rich in abietylamine and hydrogenated rosin amine containing both dihydro- 'abiet'ylamine and tetrahydroabieiwlamine when f used in combination with" ethylene oxide condensates of monoethanol rosin amines. monoethanol dehydrogenated rosin-amines, or monoethanol hydrogenated rosin amines having a molecular weight within the range of 500to about 2000. This synergistic elect is also observable in aqueous solutions of all types which" are corrosive to metals such as distilled water, tap water,

a boiler water, water used in automobile radiators with or without alcohols. glycols, and other freezing point depressants used in automobile radiators. hydrochloric acid solutions used for oil well acidizing and descaling of metals, aqueous brine solutions containing sodium chloride, mixed calcium chloride-magnesium chloride and similar brines used for refrigeration purposes, whether or not containing ammonia. It is most outstanding in the case of hydrochloric acid solutions.

The class of materials, which when used in combination with the various rosin amines gives the enhanced corrosion inhibiting effect, is a polyethylene glycol compound of the general formula RNH(CHsCHsO)1sH wherein R is the abietyl-, hydroabietyl-, or dehydroabietyl-group. Such compounds having a molecular weight of at least 500 will have a sumeiently long polyethylene glycol chain to make the useful compounds water dispersible. The value of m is thus about 5 to about 40.

The synergistic eil'ect will be noticeable with compositions having from 5 to 50% rosin amine or stabilized rosin amine in combination with a complementary amount of the polyethylene glycol compound but since rosin amine is not very soluble in water or strong mineral acids, as much as 50% of the rosin amine or stabilized rosin amine will ordinarily only be used in compositions for use in dilute acids such as 1 to 2% hydrochloric ordinarily not reduce the effectiveness of that,

part of the composition completely dispersed and cloudy dispersions will be considered as operable as long as the synergistic effect is apparent.

The amount of inhibitor composition used in aqueous solution will ordinarily be quite low. Only sufiicient to inhibit corrosion will ordinarily be used and this will vary from about 0.01% to about 5% of the aqueous solution depending upon the particular inhibitor composition. For the most active inhibitors, as may be selected from the table, the amount ordinarily used will be about 0.1 to 3% based on the weight of the aqueous solution to be inhibited.

The monoethanol rosin amine is prepared by adding the theoretical amount of ethylene oxide to the amine in the presence of a. lower alcohol solvent at a temperature of 35-100 C., and in the absence of a catalyst, and submquently distilling oil the alcohol before adding the catalyst and condensing further with ethylene oxide. If a unitary product is not desired, the use of alcohol solvent may be omitted and a temperature within therange of bio-180 C. will then be used.

The initial product of condensation of the amine with ethylene oxide is an ethanol rosin amine having. the formula where R is the organic radical of the rosin amine. The polyethylene glycol derivatives of the rosin amines of the compositions of this invention are the products of further reaction with ethylene oxide in which the alcohol groups of the initial product react with the formation of ether linkages. Thus, the product of reaction of rosin amine with seven moles of ethylene oxide by this two-step process is a substance of the general formula (cmonlolm where m equals about seven. In these formulas where R is the organic radical of a rosin amine,

it is intended that the radical shall include the abietyl radical, the dihydroabietyl radical, the tetrahydroabietyl radical, and the dehydroabietyl radical.

The rosin amines from which the glycol ethers of the monoethanol rosin amina of this invention are prepared are the primary rosin amines which are prepared by reacting ammonia with a natural rosin or a modified rosin to form the nitrile from the carboxyl group in the rosin and then hydrogenating the rosin nitrile or modified rosin nitrile to form the amine. The preparation of the nitrile may be carried out by passing gaseous ammonia into the molten rosin material and vaporizing the water as fast as it is formed in order to remove the water from the reaction mixture. Dehydration catalysts may be used to tecilitate the reaction with ammonia, if desired. The nitrile is preferably purified by neutralization or distillation to make it suitable for hydrogenation to the amine as the presence of acidic materials frequently destroys the hydrogenation catalyst. The nitrile may be formed from any natural rosin or modified rosin such as gum rosin, wood rosin, hydrogenated rosin, dehydrogenated or disproportioned rosin. or heat-treated rosin. The rosin nitriles may likewise be made from the rosin acids which are major constituents of these rosins such as abietic acid, dihydroabietic acid,

lysts and noble metal catalysts such as platinum,

palladium, palladium-on-carbon, or reduced platinum oxide. The reaction may be carried out under hydrogen pressure of from about 200 to 8000 lb./sq. in. and at a temperature of from about 20 C. to about 200 C. Solvents may be used if desired and are preferable at the lower temperatures. The hydrogenation may also be carried out in the presence of absence of ammonia. Although the hydrogenation is ordinarily carried out only to the extent of hydrogenation of the nitrile group which hydrogenates quite readily, the hydrogenation may also be carried out under such conditions of temperature. pressure, and time of hydrogenation as to hydrogenate the rosin amines which are produced to convert them to hydrorosin amines which correspond to the amines produced from hydrogenated rosin via the nitriles.

For convenience of expression in this specification, the abietyl, hydroabietyl, and dehydroabietyl radicals are referred to with the intention that they be considered broadly as covering rosin materials containing those radicals as major constituents. Thus, the products derived from rosin are considered to have the abietyl radical as a major constituent, the products derived from hydrogenated rosin are considered to have a hydroabietyl radical as the major constituent, and dehydrogenated rosin is considered to have a dehydroabietyl radical as the major constituent. Abietylamine is thus considered synonymous with rosin amine, hydroabietylamine RNH (CHzCHzO) mH having a molecular weight between about 500 and about 2000, where R is a radical selected from the group consisting of abietyl, hydroabietyl and dehydroabietyl, and m is an integer from 5 to 40.

2. A corrosion inhibitor composition for addition to aqueous solutions normally corrosive to metal surfaces consisting essentially of 5 to 50% of a dehydrogenated rosin amine and a complement of a material of the formula RNH (CHzCHzO) mH having a molecular weight between about 500 and about 2000, where R is a radical selected from the group consisting of abietyl, hydroabietyl and dehydroabiewl, and m is an integer from 5 to 40.

3. A corrosion inhibitor composition for addition to aqueous solutions normally corrosive to metal surfaces consisting essentially of 5 to 50% of a hydrogenated rosin amine and a complement of a material of the formula RHNTCHzCHzO) mH having a molecular weight between about 500 and about 2000, where R is a radical selected from the group consisting of abietyl, hydroabietyl, and dehydroabietyl, and m is an integer from 5 to 40.

4. A corrosion inhibitor composition for addition to aqueous solutions normally corrosive to metal surfaces consisting essentially of 5 to 25% of a primary rosin amine and a complement of a polyethylene glycol ether of an N-monoethanol rosin amine, the molecular weight of said ether being between about 500 and 2000.

5. A corrosion inhibitor composition for addition to aqueous solutions normally corrosive to metal surfaces consisting essentially of 5 to .of a primary dehydrogenated rosin amine and a complement ofa polyethylene glycol etherof an N-monoethanol rosin amine of molecular weight between about 500 and about 2000.

6. A corrosion inhibitor composition for addition to aqueous solutions normally corrosive to metal surfaces consisting essentially of 5 to 25% of a primary dehydrogenated rosin amine and a complement of a polyethylene glycol ether of an N-monoethanol dehydrogenated rosin amine, the molecular weight of said ether being between about 500 and 2000.

7. A corrosion inhibitor composition for addition to aqueous solutions normally corrosive to metal surfaces consisting essentially of 5 to 25% of a primary hydrogenated rosin amine and a complement of a polyethylene glycol ether of an N-monoethanol rosin amine of molecular weight between about 500 and about 2000.

8. A corrosion inhibitor composition for addition to aqueous solutions normally corrosive to metal surfaces consisting essentially of 5 to 25% I of a primary hydrogenated rosin amine and a complement of a polyethylene glycol ether of an N-monoethanol hydrogenated rosin amine, the molecular weight of said ether being between about 500 and 2000.

9. A corrosion inhibited aqueous composition comprising an aqueous solution normally corrosive toward metal surfaces selected from the group consisting of aqueous brine solutions and aqueous mineral acid solutions, said solution containing dissolved therein, in small amounts sumcientto inhibit corrosion of metal surfaces by said solution, the composition of claim 1.

10. A corrosion inhibited aqueous composition comprising an aqueous'brine solution normally corrosive toward metal surfaces containing dissolved therein, in small amounts sufllcient to inhibit corrosion of metal surfaces by said solution, the composition of claim 1.

11. A-corrosion inhibited aqueous composition comprising an aqueous mineral acid solution normally corrosive toward metal surfaces containing dissolved therein, in small amounts sufficient to inhibit corrosion of metal surfaces by said solution, the composition of claim 1.

12. A corrosion inhibited aqueous composition comprising an aqueous mineral acid solution normally corrosive toward metal surfaces containing dissolved therein, in small amounts sufllcient to inhibit corrosion of metal surfaces by said solution, the composition of claim 2.

13. A corrosion inhibited aqueous composition comprising an aqueous mineral acid solution normally corrosive toward metal surfaces containing dissolved therein, in small amounts sufficient to inhibit corrosion of metal surfaces by said solution, the composition of claim 3.

14. A corrosion inhibited aqueous composition comprising an aqueous mineral acid solution nordissolved therein, in small amounts suflicient to inhibit corrosion of metal surfaces. by said solution, the composition of claim 6.

RICHARD F. B. COX.

cns crrzn The following references are of record in the tile of this patent:

UNITED STATES PATENTS Number Name Date Krzikalla Mar. 19, 1940 Bried June 6, 1950 

1. A CORROSION INHIBITOR COMPOSITION FOR ADDITION TO AQUEOUS SOLUTIONS NORMALLY CORROSIVE TO METAL SURFACES CONSISTING ESSENTIALLY OF 5 TO 50% OF A PRIMARY ROSIN AMINE AND A COMPLEMENT OF A MATERIAL FORMULA 